Writing head producing a jet of ink



y 1969 E. AscoLl 3,458,762 I WRITING HEAD PRODUCING A JET OF INK Filed July 6, 1967 I INVENTOR gA/ZO 145mm ATTORNEY United States Patent U.S. Cl. 317-3 Claims ABSTRACT OF THE DISCLOSURE In a writing head, wherein a jet of ink is deflected by controlling electrodes, a partition surrounding the pet between the nozzle forming it and said electrodes is provided with an opening coaxial with said jet and provided with a sharp edge while the annular areas of the partition adjacent said edge are polished so as to prevent any ink droplets from forming a deposit on the partition.

Background of the invention Writing heads producing ink jets are already known, which include a tube constituting a nozzle for the ink forming the jet and jet-deflecting electrodes lying to either side of the tube axis.

Experience has shown that the ink passing out of the nozzle forms round the main jet an auxiliary or secondary emission in the shape of fine droplets starting from the nozzle and moving away from the nozzle axis along the generating lines of a surface of revolution the axis of which registers with that of the nozzle. The output of said secondary ink emission is several hundred times smaller than that of the main jet, but the ink incorporated with said secondary emission reaches different parts of the reading head and in particular the deflecting electrodes on which it forms deposits of a gradually increasing thickness. Said ink deposits modify the shape of the surfaces of the reading head in proximity with the path followed by the jet, which leads to undesirable deflections of the latter. After a certain lapse of time, said deposits may short-circuit the electrodes with each other and with the body of the ink-producing means.

Summary of the invention The present invention has for its object to cut out said drawback and covers a writing head including a body carrying the tube or nozzle forming the jet of ink and jetdeflecting electrodes located to either side of the axis of the tube while a metal disc-shaped partition extending in a direction substantially perpendicular to the axis of the jet is positioned between the nozzle and the deflecting electrodes, said partition showing an opening coaxial with the jet. This partition in the writing head producing a jet of ink is provided according to the invention with a sharp edge along the periphery of its opening while the surfaces of the partition leading to said edge are polished. This arrangement prevents any deposit of ink droplets along or near said edge.

Brief description of the drawings The accompanying drawings illustrate diagrammatically and by way of example a preferred embodiment of the invention. In said drawings:

FIG. 1 is a longitudinal sectional view of said embodiment.

FIGS. 2 and 3 are transverse cross-sections through lines IIII and IIIIII of FIG. 1.

Description of the preferred embodiment The reading head illustrated includes a metal body 1 of which the cylindrical section 2 serves as a support for a 'ice coaxial bell-shaped member 3 of insulating material. Said bell-shaped member is merely slid over said cylindrical section 2 which is provided with longitudinal slots 4 adapted to increase its elasticity. The bell-shaped member 3 may be obtained through molding and it includes a transverse partition 5 provided with an annular series of openings 6 and rigid with a sleeve-shaped coaxial member 7. Said sleeve-shaped member 7 forms a unit with the bell-shaped member 3 and may be cast for instance therewith out of a synthetic material such as that sold under the registered trade name nylon. The sleeve 7 serves as a support for a metal annulus 8 inside which is set a tube 9 forming a nozzle projecting the jet of ink. The ink is fed to the tube 9 through a yielding pipe 10.

The body 1 carries in its medial section a transverse annular partition or wall 11 provided in its middle and in registry with the tube 9 with an opening 12 the edges of which are sharp.

The end of the body 1 opposed to its cylindrical section 2 forms four longitudinal projections 13, 14, 15, 16 of which the inwardly facing surfaces are tapped at 17. Said tappings 17 allow screwing inside the body 1 an outwardly projecting terminal metal member 18 adapted to clamp in position outside the body 1 a metal ring 19, a securing plug 20 and two rings of insulating material 21 and 22 in contacting relationship with a peripheral shoulder 23 provided on the outer surface of the body 1.

The two rings 21 and 22 serve as carriers for four plates 24, 24, 25, 25' forming the electrodes deflecting the jet of ink projected out of the tube 9 through the opening 12 in the annular partition 11. The surfaces facing each other on the rings 21 and 22 are provided with grooves 21' and 22' respectively, which serve as guides for the electrode plates. As illustrated in FIGS. 1 and 3, the plates 24 and 24 are provided each with two notches 01, whereas the plates 25 and 25 show each two notches b.

The plates 24, 24', 25, 25' are furthermore given substantially the same shape and are arranged pairwise at right angles and in opposited relationship. Said arrangement allows interengaging said plates without any electric contact between them, the plates 24, 24' lying in two vertical parallel planes and the plates 25, 25' in two horizontal planes. Said interengaging plates occupy thus a minimum space in a direction parallel with the axis of the tube 9. Thus the particles of ink pass simultaneously between the horizontal deflecting plates and the vertical deflecting plates. This leads to an important advantage since, if the pairs of deflecting plates were arranged in sequence along the path of the jet of ink, this would lead to a deformation of the character drawn by it as a consequence of the time required for the progression of the particles from one pair of plates to the next. The structure disclosed thus cuts out completely said drawback.

It should be mentioned that no part of insulating material is apparent to view from any point of observation located at the end of the nozzle tube 9. As a matter of fact, said end of the tube '9 cannot possibly see the ball-shaped member 3 made of insulating material, which member is concealed by the inner annulus 8 and the outer cylindrical section 2. Similarly, the two insulating rings 21 and 22 are concealed by the annular partition 11. Thus, the electric field extending between the tube 9 and partition 11 is not subjected to the action of the electric loads which may be carried by the parts of insulating material as provided for instance by a capacitory influence.

In order to reduce as much as possible any parasitic action as a consequence of the static load carried by the insulating parts, the two rings 21 and 22 are spaced with reference to the path followed by the jet of ink by the projections 13 to 16 on the support 2 and also by the intermediate projections 26 (FIG. 3) inserted between the former projections. Thus, the jet of ink is protected to a maximum extent against any parasitic action ascribable to the static loads possibly carried by the insulating parts. Furthermore, the sole parts of the jet of ink which might be subjected to some slight action of the static loads carried by the rings 20 and 22 extend between the opening 12 and the entrance of the jet into the passage defined by the electrodes and also between the output of said passage and entrance of the opening 27 defined by the terminal metal member 18.

It should be remarked that the plates 24, 24, 25, 25 project beyond the outer periphery of the rings 21 and 22 so that it is possible to Weld thereto conducting wires adapted to give said plates the desired instantaneous voltage.

The voltage applied to the tube 9 is transmitted either by the conductive ink or else by a metal lead which may, as a matter of fact, be inserted inside the yielding pipe 10.

As soon as the difference in voltage between the partition 11 which is generally grounded and the tube 9 is sufficiently high, the ink escaping out of said tube forms a jet constituted by a succession of droplets. Said jet passing between the deflecting electrodes is shifted under the action of the voltages applied to said deflecting electrodes.

Preferably, the carrier parts made of metal, that is the parts 2, 20 and 18 are subjected to the same voltage as the support carrying the surface to be written over. Consequently, the electric field between the opening 27 in the terminal member 18 and said surface showing the point of impact for the jet of ink is equal to zero and the path of the jet of ink can therefore no longer be modified between the output of the writing head and said point of impact onto the writing surface.

The extremely small ink droplets forming the secondary jet escape within a cone the apical angle of which is large and are arrested by the partition 11. The latter is polished and the edge of the opening 12 therein is very sharp so that the droplets forming the secondary jet cannot collect on such a sharp cutting edge by reason of the surface pressure of the ink droplets. Furthermore, the sharp edge of the opening 12 merges into the surface of the partition 11 facing the tube 9 along a convex annular surface 11a which is also polished so as to further the coalescence of the extremely small ink droplets which may settle on said annular surface. Said droplets form thus a continuous annular sheet of ink which flows steadily towards an output port opening into the depending tube 28 as furthered by a vertical groove 29 extending between the convex surface 11a and said output port.

The above-described writing head shows numerous advantages over those proposed hitherto. Asa matter of fact, said head is of a simple structure and shows a high rigidity. Furthermore, it forms a closed unit and the weak sections of said head are protected against shocks and the like objectionable actions.

By reason of the shield formed by the metal parts carrying the head, the electric fields inside said head remain always uniform and their values are well-defined. Said fields can be deformed neither by outer parasitic fields, nor under the action of the static loads which may collect on the insulating parts.

The openings 6 formed in the partition allow air to enter the writing head so as to replace the air escaping through the opening 27 and which is carried along by the moving jet of ink. Thus, the air pressure inside the head remain-s substantially constant which is essential with a view to obtaining a clean writing.

The system of carrier parts is rigid with the securing lug 20 as provided by the mere screwing of the terminal member 18 inside the threads 17 cut in the longitudinal projections 13 to 16. T 0 this end, the terminal member 18 is provided along its outer edge with a slot 29' adapted to be engaged by a screw-driver. Furthermore, the insulating bell-shaped member 3 rigid with the annulus 8 and tube 9 may be removed through a mere sliding over the cylindrical section 2 of the body 1 which allows inspecting and cleaning easily said tube 9.

I claim:

1. In a writing head comprising a tubular support, a nozzle adapted to produce a jet of ink the direction of which is parallel with the axis of the support and deflecting electrodes facing the location of a fraction of the jet, the provision of a disc-shaped partition extending across the location of the jet lying between the outlet of the nozzle and the first-mentioned fraction and showing an opening coaxial with the jet and provided with a sharp edge, the surfaces of the partition adjacent said edge being polished.

2. A writing head as claimed in claim 1, wherein the surface of the partition facing the nozzle is fiat and merges into the sharp edge of the opening along an annular convex area.

3. A writing head as claimed in claim 1, wherein the surface of the partition facing the nozzle is flat and merges into the sharp edge of the opening along an annular convex area and the surface of the partition facing away from the nozzle is coplanar with said edge.

4. A writing head as claimed in claim 1, wherein the surface of the partition facing the nozzle is flat and merges into the sharp edge of the opening along an annular convex area, said surface facing the nozzle being provided with a radial vertical groove extending downwardly from the periphery of the annular convex surface.

5. A writing head as claimed in claim 1, wherein the surface of the partition facing the nozzle is flat and merges into the sharp edge of the opening along an annular convex area, said surface facing the nozzle being provided with a radial vertical groove extending downwardly from the periphery of the annular convex surface, and means at the bottom of said groove being adapted to collect the ink droplets impinging on said surface facing the nozzle and running down along said groove.

References Cited UNITED STATES PATENTS 2,600,129 6/ 1952 Richards 118-629 3,275,239 9/ 1966 Oesterle 239-3 3,278,940 10/1966 Ascoli 346- 3,060,429 10/1962 Winston 346-75 LEE T. HIX, Primary Examiner D. I-IARNISH, Assistant Examiner US. Cl. X.R. 239-15; 346-75 

